The nuanced finding suggests the agency believes the totality of evidence makes a lab origin more likely than a natural origin.

The problem for the lab-leak position is that the U.S. has never had access to the Wuhan lab and has thus been unable to reach a definitive answer for more than five years. Now that the CIA has at last come to a conclusion, not all scientists are sold on what it has reported, seeing the results as thinly scientifically sourced.

A new analysis that began under the Biden administration is released by the C.I.A.’s new director, John Ratcliffe, who wants the agency to get “off the sidelines” in the debate.

The Central Intelligence Agency on Saturday said it has shifted its previous assessments and has concluded that it’s likely the Covid-19 virus was leaked from a Chinese lab before it became a global pandemic but added that the agency had “low confidence” in its judgment.

The intelligence agency says it has a “low confidence” in its new finding, but this is further than it has ever gone in pinpointing the origin of a virus that killed millions worldwide.

The CIA now assesses the virus that causes Covid-19 more likely originated from an accidental lab leak in China, rather than occurring naturally, according to a statement from the agency Saturday, just days after Director John Ratcliffe took the reins.

Several US agencies and some scientists have proposed the lab leak theory over the past few years. But other experts insist there are good reasons to think the devastating pathogen emerged from a market where animals are traded.